(UNDATED) - The National Weather Service has declared a Winter Storm Warning for five southwest Indiana counties and a Winter Weather Advisory for an additional 29 southern Indiana counties.

Two to 4 inches of accumulating snow is forecast for southern Indiana through Wednesday with 1 to 2 inches predicted for central Indiana. Northern Indiana may see a dusting to 1 inch of snow.

During business hours today, Indiana Department of Transportation mechanics are servicing yellow plow trucks, and in some areas salt-brine tankers are spraying bridges and heavily-traveled state highways.

Indiana Department of Transportation maintenance supervisors are closely monitoring evolving local forecasts, and will deploy yellow plow trucks before snow and ice begin to accumulate on Indiana's interstates, U.S. highways and state routes. Trained employees are on call to staff plow trucks around the clock with alternating shifts of 12 hours or more.

As there are changes in forecasted and observed road conditions, local INDOT staff will adjust its call-out of manpower, trucks and materials and shift resources as appropriate.

Morning commute

INDOT's yellow plow trucks will clear as much snow from state highways as possible in the hours before the Wednesday morning commute, when the heaviest snow is forecast. Each plow route takes 2-3 hours to complete with salt assisting in melting between passes.

Commuters should reschedule optional trips with work or school before leaving today and plan extra travel time on Wednesday morning. Drivers who encounter a plow at work in rush-hour traffic should pull aside and allow the truck to proceed on its route unimpeded - remember "Don't crowd the plow".

Drivers may see plows working in tandem on multi-lane state highways. Traffic should not attempt to pass plow trucks if all lanes are blocked, but stay a safe distance and speed behind. Plow trucks move at 45 mph or less when plowing or salting their routes, and road conditions are always safer behind a plow at work than in front.

Low temperatures

With temperatures remaining well below freezing, road salt has to work harder to melt snow and ice. Granular salt helps to add traction while lowering the temperature at which the ice melts. INDOT may mix road salt with sand or specialty chemicals that help it work more effectively in these conditions.

Sub-freezing temperatures increase the chances of melt-water refreezing into "black ice" or "slick spots" that may be difficult for drivers to distinguish from dry pavement. Areas that receive less direct sunlight are common places for slick spots. Even four-wheel-drive vehicles and large trucks are no match if all tires are on ice.

There are several steps that drivers can take to minimize the risk of losing control on snow-covered or icy roads:

Consult local weather forecasts to determine the latest timing and location of the storm.